The present invention relates to an improved valve train for an internal combustion engine, and more particularly, to a valve deactivator assembly for use therein.
Although the valve deactivator assembly of the present invention may be utilized to introduce some additional lash into the valve train, such that the valves open and close by an amount less than the normal opening and closing, the invention is especially suited for introducing into the valve train sufficient lash (also referred hereinafter as "lost motion"), such that the valves no longer open and close at all, and the invention will be described in connection therewith.
Valve deactivators of the general type to which the invention relates are known, especially in connection with internal combustion engines having push rod type valve gear train in which there is a rocker arm, with one end of the rocker arm engaging a push rod, and the other end engaging the engine poppet valve. Typically, a central portion of the rocker arm is fixed relative to the cylinder head (or other suitable structure) by a fulcrum arrangement as is well known to those skilled in the art, in which the fulcrum normally prevents movement of the central portion of the rocker arm in an "up and down" direction. At the same time, the fulcrum permits the rocker arm to engage in cyclical, pivotal movement, in response to the cyclical motion of the push rod, which results from the engagement of the push rod with the lobes of the rotating camshaft.
There are a number of known valve deactivator assemblies which are operably associated with the fulcrum portion of the rocker arm and which, in the latched condition, restrain the fulcrum portion of the rocker arm to move in its normal cyclical, pivotal movement. However, in an unlatched condition, the valve deactivator assembly permits the fulcrum portion of the rocker arm to engage in "lost motion" such that the cyclical, pivotal movement of the push rods causes the rocker arm to undergo cyclical, pivotal movement about the end which is in engagement with the engine poppet valve. In other words, the rocker arm merely pivots, but the engine poppet valve does not move and hence, is in its deactivated condition.
Although the known valve deactivator assemblies of the type referred to above have performed in a generally satisfactory manner, such assemblies do add substantially to the overall cost of the valve gear train, and in many cases, also add undesirably to the space taken up by the overall rocker arm installation. In some engine designs, there is simply no room to add a valve deactivator assembly to the rocker arm.
Typically, in a push rod type of valve gear train, there is some sort of cam follower device having one portion thereof in engagement with the cam lobe on the engine cam shaft, and another portion thereof in engagement with the lower end of the push rod. It is also known for such a cam follower mechanism to include a hydraulic lash compensation element.
It has been recognized by those skilled in the art as being desirable to incorporate the valve deactivator assembly into the cam follower, thus eliminating the need for adding a substantial, expensive, space consuming structure to the rocker arm assembly. However, in many engines, it would not be acceptable to increase substantially the size of the cam follower, in order to incorporate therein a valve deactivator assembly.